Former US President Barack Obama's family dog Bo, a male Portuguese Water Dog with a mop of black and white fur who became a familiar playful sight around the White House, has died.

Obama announced the death late on Saturday, saying the dog had been "a constant, gentle presence in our lives - happy to see us on our good days, our bad days and everyday in between."

"We will miss him dearly," he said on Twitter.

His wife Michelle Obama said in a separate tweet that Bo, 12, had been suffering from cancer.

Bo came to the White House in 2009 soon after the start of Obama's first term and was joined a few years later by a female of the same breed called Sunny.

Obama, who left office in 2017, praised Bo's calm demeanor in the White House, saying the dog "had a big bark but no bite, loved to jump in the pool in summer, was unflappable with children, lived for scraps around the dinner table, and had great hair."